Title: INTRODUCTION TO ANIMAL DIVERSITY
1INTRODUCTION TO ANIMAL DIVERSITY
- Chapter 32
- Our Kingdom
- We are Animals
2Animals Are
- Species-rich
- Morphologically diverse lineage of multicellular
organisms on the tree of life - Distinguished by two traits
- they eat
- they move
- The largest and most abundant predators,
herbivores, and detritivores
3Animals Are
- Multicellular, heterotrophic eukaryotes
- Heterotrophs
- ingest food
- find food by tunneling, swimming, filtering,
crawling, creeping, slithering, walking, running,
or flying. - Dominant consumers in both aquatic and
terrestrial habitats - Animal cells lack cell walls
- Distinguished by two tissues
- Nervous tissue and muscle tissue
- Most animals reproduce sexually with the diploid
stage usually dominating the life cycle
4Methods in the Study of Animals
- Analyzing Comparative Morphology
- The Evolution of Tissues
- Symmetry and Cephalization
- Evolution of a Body Cavity
- The Protostome and Deuterostome Patterns of
Development - The Tube-within-a-Tube Design
- A Phylogeny of Animals Based on Morphology
- Using the Fossil Record
- Evaluating Molecular Phylogenies
5Themes in the Diversification of Animals
- Suspension (Filter) Feeding
- Deposit Feeding
- Herbivory
- Predation
- Parasitism
- FeedingMovement
- Types of Limbs Unjointed and Jointed
- Are All Animal Appendages Homologous?
- Reproduction and Life Cycles
6Key Lineages of Animals
- Choanoflagellates (Collar Flagellates)
- Porifera (Sponges)
- Cnidaria (Jellyfish, Corals, Anemones, Hydroids,
Sea Fans) - Ctenophora (Comb Jellies)
- Acoelomorpha
7Monophyletic and Very Diverse
- The animals are a monophyletic group
- Animals are very diverse
- 34 major animal phyla are recognized
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10Analyzing Comparative Morphology
- Most morphological diversity in animals is based
on - differences in mouths and limbs
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14Basic Architecture
- Four features define an animal's body plan
- the number of tissue types in embryos
- the type of body symmetry
- the presence or absence of a fluid-filled cavity
- the way in which the earliest events of embryo
development proceed
15The Evolution of Tissues
- All animals other than sponges have tissues
- tightly integrated structural and functional
units of cells. - Diploblasts
- embryos have two types of tissues or germ layers
- Ectoderm
- Endoderm
- Triploblasts
- embryos have three types of tissues
- Ectoderm
- Endoderm
- Mesoderm
- germ layers develop into distinct adult tissues
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19Symmetry and Cephalization
- A basic feature of a multicellular body is the
presence or absence of a plane of symmetry - radial symmetry
- at least two planes of symmetry.
- bilateral symmetry
- a single plane of symmetry
- face their environment in one direction.
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21Cephalization
- Bilateral symmetry allowed
- Evolution of a head, or anterior region, where
structures for feeding, sensing the environment,
and processing information are concentrated
22Evolution of a Body Cavity
- Animals may or may not have an internal,
fluid-filled body cavity - coelom
- forms from within the mesoderm
- lined with cells from the mesoderm
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24Advantages of a Coelom
- Creates a medium for circulation
- Makes space for internal organs
- A hydrostatic skeleton
- fluid-filled chamber
- allows movement
- even without fins or limbs.
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27The Protostome and Deuterostome Patterns of
Development
- Coelomates are bilaterally symmetric
- except echinoderms
- three embryonic tissue layers
- Bilatera
- protostomes
- arthropods, mollusks, and segmented worms
- deuterostomes
- vertebrates and echinoderms
28Differences in Early Development
- Three events in early development differ in
protostomes and deuterostomes - Cleavage
- Gastrulation
- coelom formation
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30Cleavage
- Rapid series of mitotic divisions
- Spiral cleavage
- mitotic spindles of dividing cells orient at an
angle to the main axis of the cells - resulting in a helical arrangement
- Radial cleavage
- mitotic spindles of dividing cells orient
parallel or perpendicular to the main axis of the
cells - resulting in a pattern of cells stacked directly
on top of each other
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33The Tube-within-a-Tube Design
- The basic animal body plan is a
tube-within-a-tube design in which the outer tube
forms the body wall and the inner tube forms the
gut
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35Ancestor?
- The animal kingdom all developed from a common
ancestor ( monophyletic) probable during the
Precambrian era. -
- Probably a colonial choanoflagelate that lived
about700 million years ago. Modern
choanoflagellates are tiny, have a stalk and live
in ponds and lakes) - A hypothesis of animal origin from flagellated
protists says that the colony of cells in the
protist evolved into a sphere and then
differenciated and especialized creating two
layers of cells.
36The common ancestor of living animals
- May have lived 1.2 billion800 million years ago
- May have resembled modern choanoflagellates,
protists that are the closest living relatives of
animals
Figure 32.3
37closest living relatives of animals
- a colonial, flagellated protist
Figure 32.4
38A Phylogeny of Animals Based on Morphology
- The phylogenetic tree indicates that a group of
protists called the choanoflagellates are the
closest living relatives of animals and that the
Porifera (sponges) are the most ancient animal
phylum.
39Phylogeny Based on Morphology
40- Radially symmetric phyla are placed on the tree
next because their tubelike body plans are
relatively simple. Among the bilaterally
symmetric phyla, the acoelomates and
pseudocoelomates appeared first, followed by the
coelomates.
41- Two major events occurred after the coelomates
split into the protostomes and deuterostomes - radial symmetry evolved
- segmentation evolved independently in both
lineages of coelomates.
42Using the Fossil Record
- Most major groups of animals appear in the
fossil record starting about 580 million years
ago - The fossil record is generally consistent with
the morphological phylogeny.
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45Neoproterozoic Era (1 Billion524 Million Years
Ago)
- Early members of the animal fossil record are
known as the Ediacaran fauna( first fossils of
animals about 575 mya). Simple radial forms and
segmented bodies with legs.
Figure 32.5a, b
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47Paleozoic Era (542251 Million Years Ago)
- The Cambrian explosion marks the earliest fossil
appearance of many major groups of living animals - Is described by several current hypotheses such
as predator- prey relationships, oxygen increase
and evolution of the hox genes
Figure 32.6
48Mesozoic Era (25165.5 Million Years Ago)
- During the Mesozoic era
- Dinosaurs were the dominant terrestrial
vertebrates - Coral reefs emerged, becoming important marine
ecological niches for other organisms - The first mammals appeared (tiny, nocturnal
insect eaters
49Cenozoic Era (65.5 Million Years Ago to the
Present)
- The beginning of this era
- Followed mass extinctions of both terrestrial and
marine animals - Modern mammal orders and insects
- diversified during the Cenozoic
- Also flowering plants appeared
50Evaluating Molecular Phylogenies
- The phylogenetic tree based on genes for
ribosomal RNA and several proteins
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52Points of Agreement
- All animals share a common ancestor
- Sponges are basal animals (branch from the base
of tree, no tissues) - Eumetazoa is a clade of animals with true tissues
- Most animal phyla belong to the clade Bilateria
- Vertebrates belong to the clade Deuterostomia
53Disagreement over the Bilaterians
- The morphology-based tree
- Divides the bilaterians into two clades
deuterostomes and protostomes - In contrast, recent molecular studies
- assign two sister taxa to the protostomes rather
than one the ecdysozoans and the lophotrochozoans
54Important Observations Emerge From the Data
- The most ancient triploblasts lacked a coelom
- The major event in the evolution of the Bilateria
was the split between protostomes and
deuterostomes - Segmentation evolved independently in the
annelids and the arthropods and - Pseudocoeloms arose from coeloms twice in
evolutionary history
55Phylogenetic trees are best described as
- true and inerrant statements about evolutionary
relationships. - hypothetical portrayals of evolutionary
relationships. - the most accurate possible representations of
genetic relationships among taxa. - theories of evolution.
- the closest things to absolute certainty that
modern systematists can produce.
56Themes in the Diversification of Animals
- Within the phylum
- basic features of the body plan do not vary from
species to species - Diversity arose
- mostly because of the evolution of innovative
methods for feeding and moving
57Feeding
- The feeding tactics observed in animals can be
broken into five general types - suspension feeding
- deposit feeding
- herbivory
- predation
- Parasitism
- Many animals undergo a metamorphosis
- a change in form during development
- allows juveniles and adults to exploit different
sources of food
58Suspension (Filter) Feeding
- Suspension feeders, or filter feeders, capture
food by filtering out particles suspended in
water or air - This method is found in a wide variety of animal
groups and has evolved many times independently
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62Deposit Feeding
- Deposit feeders eat their way through a
substrate - Food
- soil-dwelling bacteria, protists, fungi, and
archaea - detritusthe dead and partially decomposed
remains of organisms - Depending on food
- herbivores (plant eaters), parasites,
detritivores (detritus eaters), or predators
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64Herbivory
- Herbivores
- animals that digest algae or plant tissues
- complex mouths with structures that make biting
and chewing or sucking possible
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69Predation
- Sit-and-wait predators rarely move at all until
prey is captured - stalkers pursue their prey
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72Parasitism
- Parasites are much smaller than their victims
and often harvest nutrients without causing death - Endoparasites
- live inside their hosts
- often wormlike in shape
- can be extremely simple morphologically
- Ectoparasites
- live outside their hosts
- usually have grasping mouthparts
- pierce the hosts exterior and suck the
nutrient-rich fluids inside
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75Movement
- Many animals are sit-and-wait predators, and
some are sessile throughout their adult lives.
But the vast majority of animals move under their
own power either as juveniles or as adults.
76Function of Movement
- three functions in adult animals
- Finding food
- finding mates
- escaping from predators.
77Limbs
- A major innovation in animals
- made highly controlled, rapid movement possible
- Two types
- Unjointed
- saclike
- Jointed
- move when muscles that are attached to a skeleton
contract or relax
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82Homologous vs Non-Homologous
- Biologists have argued that at least a few of
the same genes are involved in the development of
all appendages observed in animals - Hypothesis is that all animal appendages have
some degree of genetic homology - that they are all derived from appendages that
were present in a common ancestor. - This hypothesis is controversial, however, and
research continues
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84Reproduction and Life Cycles
- At least some species in most animal phyla can
reproduce asexually (via mitosis), as well as
sexually (via meiosis). - Sexual reproduction can occur with internal or
external fertilization
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87Development
- Eggs or embryos may be retained in the females
body during development - viviparous
- May be laid outside the body
- oviparous
- Female retains eggs inside her body during early
development - embryos are nourished by yolk inside the egg and
not by nutrients transferred directly from the
mother - ovoviviparous
- Vast majority of animals are oviparous
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90Development
- After a sperm fertilizes an egg
- The zygote undergoes cleavage, leading to the
formation of a blastula - The blastula undergoes gastrulation
- Resulting in the formation of embryonic tissue
layers and a gastrula
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- Early embryonic development in animals
Figure 32.2
92Metamorphosis
- The change from juvenile to adult body type
- Larva
- juvenile individual
- looks substantially different from the adult
- Nymph
- juvenile individual
- looks like a miniature adult
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94Pupation
- When a larva has grown sufficiently, it secretes
a protective case and is now known as a pupa
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96Into an Adult
- During pupation, the pupas body is completely
remodeled into a new, adult form
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98Holometabolous
- Complete metamorphosis
- two-step process
- from larva to pupa to adult
- involving dramatic changes in morphology and
habitat use
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100Hemimetabolou
- Incomplete metamorphosis
- One-step process of sexual maturation.
- Limited morphological difference between juvenile
and adult
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102Marine Animals
- Complete metamorphosis
- extremely common in marine animals
- most cnidarians have two distinct body types
during their life cycle - a largely sessile form called a polyp
- alternates with a free-floating stage called a
medusa
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